Spirit level

ABSTRACT

A spirit level has a hollow profile member as the spirit level body and at least one bubble level with a bubble level holder. The bubble level holder is mounted moveably in the spirit level body, and the bubble level holder has an opening into which a fixing means can be introduced through a wall of the spirit level body. The fixing means prevents a displacement of the bubble level holder parallel to the longitudinal axis of the spirit level body, and allows a movement of the bubble level holder normal to a measurement surface of the spirit level body.

The invention concerns a spirit level having the features of the classifying portion of claim 1.

Spirit levels are frequently subjected to severe temperature fluctuations in use. The difference in the coefficients of thermal expansion between a spirit level body which is usually made from aluminum and a bubble level body which is generally made from plastic or a bubble level holder gives rise to thermal stresses and thermal expansion phenomena between the spirit level body and the bubble level body or the bubble level holder. It is particularly disadvantageous if the relative movement of the bubble level body or bubble level holder and the spirit level body leads to a loss in the calibration position of the bubble level.

Approaches for overcoming that technical problem are known from the state of the art.

Thus WO 7900672 discloses a spirit level whose bubble level is displaceable by an adjusting device in an accommodating space in the housing relative to a measurement surface. By virtue of the fact that the closure body which accommodates the adjusting device is in the form of a separate part the material thereof and thus its coefficient of thermal expansion can be so selected that a difference in thermal expansion between the bubble level and the housing is compensated.

The object of the present invention is to provide a spirit level with compatibility in relation to temperature fluctuations, that is improved over the state of the art, and with a simple structure.

That object is attained by a spirit level having the features of claim 1. Advantageous configurations are recited in the appendant claims.

The fact that the bubble level holder is mounted moveably in the spirit level body and the bubble level holder has an opening into which a fixing means can be introduced through a wall of the spirit level body, wherein the fixing means prevents displacement of the bubble level holder parallel to the longitudinal axis of the spirit level body and allows a movement of the bubble level holder normal to a measurement surface of the spirit level body provides improved compatibility of the spirit level in relation to temperature fluctuations.

The expression compatibility in relation to temperature fluctuations is used here to mean that the spirit level preserves a high degree of accuracy when being involved in temperature fluctuations.

To retain a high degree of accuracy for the spirit level when it is involved in temperature fluctuations therefore the apparently paradoxical measure is adopted of mounting the bubble level holder moveably in the spirit level body.

When a change in temperature occurs high stresses occur between the spirit level body and the bubble level holder, whereby the calibration position of the bubble level can be lost.

In experiments the applicant found that, with a moveable mounting for the bubble level holder in the spirit level body, only low stresses occur between the bubble level holder and the spirit level body and thus there is no loss of a calibration position of the spirit level.

In contrast fixing methods using adhesive or pressing of the bubble level holder in the spirit level body are detrimental in terms of compatibility of the spirit level in relation to temperature fluctuations. Here more specifically no relative movement is possible between the bubble level holder and the spirit level body.

The opening in the bubble level holder forms a guide for the fixing means so that a relative movement of the bubble level holder in the spirit level body along a direction normal to the measurement surface of the spirit level body is permitted.

The fixing means can be introduced by way of a wall of the spirit level body. For that purpose provided in at least one wall of the spirit level body is an aperture, by way of which the fixing means can be introduced through the wall of the spirit level body into the opening in the bubble level holder.

To make the spirit level insensitive to shocks as can occur for example when a spirit level is dropped it is necessary for the bubble level holder to be fixed in relation to displacement on the longitudinal axis of the spirit level body.

The at least one aperture for introduction of the fixing means is preferably provided at a side surface (cheek surface) of the spirit level body. That means that surface which forms the long side, in a cross-section through the profile forming the spirit level body.

It can alternatively be provided that the at least one aperture is provided at a narrow side of the spirit level body. In that case the corresponding opening in the bubble level holder can be formed by a bore normal to a measurement surface. The fixing means can be formed as sliding in the bore.

Because the at least one aperture is of such tolerance with the fixing means that the fixing means is pressed in the aperture no further securing of the fixing means is required.

The measurement surface of a spirit level is formed by the outside wall of the narrow side of the profile member forming the spirit level body, on the side opposite to the flat bubble level (horizontal bubble level). When a usual rectangular cross-section is involved that is therefore a narrow side of the rectangular profile.

It can be provided that the fixing means is in the form of a sleeve. The term sleeve is used to denote a profile member of hollow cross-section.

It can be provided that the fixing means is in the form of a stud. In this variant the fixing means has a filled cross-section.

It can be provided that the fixing means is in the form of a two-part pin member with snap-action catches, wherein the halves of the two-part pin member can be introduced through oppositely disposed walls of the spirit level body and can be fixed together by snapping of the snap-action catches.

It is preferably provided that the opening in the bubble level holder is in the form of a slot. The slot serves as a guide element for the fixing means which can be inserted. In that arrangement the longitudinal extent of the slot extends in such a way as to permit a movement of the bubble level holder normal to the measurement surface of the spirit level body.

It should be mentioned that for fixing bubble level holders in the spirit level body, it is known to use so-called nail sleeves. Nail sleeves are bodies in the form of a cylindrical ring, which are pressed into the spirit level body, being pressed into a bore in the bubble level holder. In tests conducted by the applicant however it has been found that, when temperature changes occur, a nail sleeve has a detrimental effect on the accuracy of the spirit level. More specifically if the bubble level holder performs a relative movement, caused by thermal expansion, in the spirit level body along an axis normal to a measurement surface of the spirit level then a nail sleeve can act as a pivot point in relation to the bubble level holder and thus add a rotational movement to the purely translatory movement caused by the thermal expansion. That rotational movement means that the calibration position of the bubble level is lost.

The provision however of a guide which prevents a displacement of the bubble level holder parallel to the longitudinal axis of the spirit level body and allows a movement of the bubble level body normal to a measurement surface of the spirit level body means that the above-described negative effect when thermal expansion takes place does not occur and the bubble level retains its calibration position.

It is preferably provided that the bubble level holder is fixed in the spirit level body by way of at least one spring. The at least one spring presses the bubble level holder against the inside wall of the spirit level body. Preferably the bubble level holder is braced in the spirit level body between the narrow sides of the profile member forming the spirit level body. Fixing by way of a spring allows a movement of the bubble level holder, as described hereinbefore. The spring can be for example in the form of a leaf spring or a coil spring. A plurality of springs can be provided.

The invention is particularly suitable for round bubble levels, that is to say those bubble levels which serve for reading off the vertical orientation of the spirit level (vertical bubble levels). Round bubble levels generally involve a can-shaped, that is to say cylindrical, configuration.

The invention is described in greater detail by reference to the following Figures in which:

FIG. 1 shows a section of a spirit level according to the state of the art,

FIG. 2 shows a spirit level in a first embodiment,

FIG. 3 shows a bubble level holder in an embodiment, and

FIGS. 4a through 4c show a fixing means in an embodiment.

FIG. 1 shows a spirit level 1 according to the state of the art. The spirit level 1 has two plane-parallel measurement surfaces 9. A bubble level holder 4 is clamped in the spirit level body 2 by being oversize in relation thereto and is possibly additionally glued in place. The bubble level holder 4 is here secured against displacement on the longitudinal axis in the spirit level body 2 by a nail sleeve 21. Also indicated is the bubble level 1, here in the form of a round bubble level, which is fitted into the bubble level holder 4. When temperature fluctuations occur there is the danger of the bubble level 3 losing its calibration position as a tilting moment can occur with respect to the nail sleeve 21.

FIG. 2 shows a first embodiment of the spirit level 1 according to the invention. The bubble level holder 4 is braced in relation to the inside wall of the spirit level body 2 by way of a spring 19 (here in the form of a leaf spring).

An opening 23 in the bubble level holder 4 is in the form of a slot. A fixing means 8 is introduced into the opening 23 through the walls of the spirit level body 2. Thus, when thermal expansion occurs between the spirit level body 2 and the bubble level holder 4, a relative movement of the bubble level holder 4 can take place along the guide formed from the opening 23 and the fixing means 8 without a tilting moment being imparted to the bubble level holder 4. The direction of movement of the bubble level holder 4, as can be caused by thermal expansion within the spirit level body 2, is indicated by a solid black arrow. For the sake of completeness a section A-A through the spirit level body 2 is shown, which in the present embodiment is of a rectangular hollow profile.

FIG. 3 shows a possible configuration of the bubble level holder 4. The bubble level holder 4 has a first orifice 18 for receiving a bubble level 3. Also provided on the bubble level holder 4 is a receiving means 20 for one or more springs 19 (not shown here). The bubble level holder 4 can be braced against the inside wall of a spirit level body 2 by way of the spring or springs 19. In the present example the receiving means 20 is designed for the insertion of a leaf spring. A spirit level body 2 is indicated in broken line in order to clearly show the installation position of the bubble level holder 4.

Fixing means 8 (not shown here) can be inserted into the openings 23 in the installation position of the bubble level holder 4 through corresponding apertures in the spirit level body 2. The openings 23 are in the form of slots, the longitudinal axis of the opening 23 being transverse relative to the longitudinal axis of the spirit level body 2. In that way the bubble level holder 4 is mounted in the spirit level body 2, in a way which allows a free movement of the bubble level holder 4 in the event of thermal expansion (direction of movement indicated by the solid black arrow) while at the same time the bubble level holder 4 is secured against displacement in the longitudinal direction of the spirit level 1 (for example in the event of shocks).

As the movements to be expected by virtue of thermal expansion are very slight (a few 1/10ths of a millimeter) the longitudinal extent of the openings 23 can be only little greater than their width.

The spring or springs 19 are preferably made of metal, preferably steel. Metal springs have better long-term stability and maintain the spring force, in comparison with springs of plastic.

Adjustment of a bubble level 3 in the bubble level holder 4 can be effected prior to or after installation.

FIGS. 4a through 4c show various views of a fixing means 8 in the form of a two-part stud 12. A respective half is shown. In the illustrated embodiment the studs 12 also form a cover 17 for the bubble level 3.

The studs 12 can be introduced by way of suitable apertures in the spirit level body 2 into the opening 23 (see in that respect for example FIG. 3) and can be connected together by way of snap-action catches 13.

LIST OF REFERENCES

1 spirit level 2 spirit level body 3 bubble level 4 bubble level holder 8 fixing means 9 measurement surface 12 stud 13 snap-action catch 17 cover 18 orifice 19 spring 20 receiving means 21 nail sleeve 

1. A spirit level comprises a hollow profile member as the spirit level body and at least one bubble level with a bubble level holder, wherein the bubble level holder is mounted moveably in the spirit level body and the bubble level holder has an opening into which a fixing means can be introduced through a wall of the spirit level body, wherein the fixing means prevents a displacement of the bubble level holder parallel to the longitudinal axis of the spirit level body and allows a movement of the bubble level holder normal to a measurement surface of the spirit level body.
 2. A spirit level as set forth in claim 1, wherein the fixing means is in the form of a sleeve.
 3. A spirit level as set forth in claim 1, wherein the fixing means is in the form of a stud.
 4. A spirit level as set forth in claim 1, wherein the fixing means is in the form of a two-part pin member with snap-action catches, wherein the halves of the two-part pin member can be introduced through oppositely disposed walls of the spirit level body and can be fixed together by snapping of the snap-action catches.
 5. A spirit level as set forth in claim 1, wherein the opening is in the form of a slot.
 6. A spirit level as set forth in claim 1, wherein the bubble level holder is fixed in the spirit level body by way of at least one spring.
 7. A spirit level as set forth in claim 1, wherein the bubble level is in the form of a vertical bubble level of the spirit level. 